Importance: This indicates Greg's immaturity and lack of understanding about things. He thinks that they haven't gone anywhere because his parents have no interest, rather than considering that his parents couldn't get time off from work, or that they didn't have the money to go.

Then I remembered: I still had the Cheese Touch from last year." -- Greg
(September paragraph 30)

Importance: This refers back to book one where Greg touched the cursed piece of cheese. Once he "hands" off the "touch" to another student, he's relieved of the curse...